Est. 1919 · Tokyo, Japan (Ricoh Imaging Company since 2011) · 18 lenses
Asahi Optical Joint Stock Co. was founded in November 1919 in the Toshima district of Tokyo, originally to produce spectacle lenses. By 1923 the company had begun supplying camera lenses to other Japanese manufacturers (including Konishiroku and the early Olympus), establishing itself as one of Japan's first specialist optical-glass workshops. The Asahiflex (1952) was Japan's first 35 mm single-lens reflex camera, and its successor — the Asahiflex IIB (1954) — introduced the instant-return mirror, a feature that would soon become standard across the SLR industry.
The Asahi Pentax (1957) gave the brand its enduring name, derived from 'PENTAprism' (the eye-level prism finder it inherited from Contax/East German tradition) and the bayonet-derived 'contAX' suffix. Pentax adopted the M42 'Praktica' screw mount and built up a wide lens line under the Takumar and later Super-Takumar / SMC Takumar names. The Spotmatic (1964) popularized through-the-lens (TTL) stop-down metering at consumer prices, and the SMC (Super Multi Coating) treatment introduced in 1971 set a multi-layer anti-reflection benchmark that influenced every coating program that followed.
In 1975, Pentax replaced the M42 screw mount with the K-mount bayonet — explicitly licensed as an open standard, with Ricoh, Chinon, Cosina, and others adopting it. The K-mount has remained mechanically and optically compatible across more than four decades, from the K1000 manual SLR (1976) through modern Pentax K-1 II full-frame DSLRs. The LX (1980) was Pentax's modular professional SLR, and the company was equally serious about medium format: the 6×7 (1969, modernized as the 67 II in 1998) and the autofocus 645 / 645N / 645D / 645Z (1984–2014) carried the Pentax name into the studio and landscape markets.
Asahi Optical Co. renamed itself Pentax Corporation in 2002. Hoya acquired Pentax in 2007, primarily for its medical-endoscope business, and in 2011 sold the imaging division to Ricoh — forming Ricoh Imaging Company, Ltd., while Hoya retained the medical-optics operations. Under Ricoh, Pentax has continued as a deliberately independent DSLR and medium-format brand: the K-3 III APS-C and K-1 II full-frame DSLRs, the Pentax 645Z medium-format DSLR, and the renowned DA Limited compact prime series (DA 21 mm, 40 mm, and 70 mm Limited) recognized for their all-metal barrels and distinct rendering character.
Notable designs: Super-Takumar 50mm f/1.4, SMC Takumar 35mm f/2, SMC Pentax-A* 85mm f/1.4, SMC Pentax-FA 31mm f/1.8 AL Limited, smc Pentax-DA 21mm f/3.2 AL Limited, HD Pentax-D FA* 50mm f/1.4 SDM AW